To add to my comment
the very notion that Hashem “worked” and “rested” are obviously not literal. Hashem speaks in a way that we understand, and we commemorate what we are told using human expressions and practices.
So IF Hashem created the world in 6 “days” lasting 6 billion years. IT would be nonsensical to commemorate this by keeping 6 billion years of weekday Rather we commemorate it using human terms of literal days. Just as we observe by resting even if this is different than Hashem’s “resting”
UJM’s questions are harder to dismiss, and I don’t have a good answer